In the overviews-specialized dataview classes the sql-generating
functions had an unneeded parameter filters.
In some cases, since this parameter was not being paaased from
the base dataviews class it was masking the override parameter.
This value would ideally be adjusted to prevent the grid size of the
overview used being greater that one pixel. So, this should be the
larger dimension of the map window in pixels.
Javier Goizueta